Valves of this type can be used as pressure relief valves or as suction relief valves. A pressure relief valve is always described hereinafter by way of example. The same also applies analogously however for suction relief valves.
With a generic pressure relief valve, the pressure in a container is prevented from rising above a predetermined response pressure. In the closed position, the valve plate bears against the valve seat via the valve plate face and thus seals the valve. If the pressure in the container, which is located beneath the valve seat, then rises above the response pressure, the force acting on the valve plate as a result of the pressure is large enough to bring the valve plate from the closed position into the pass-through position. The valve is thus opened and a pressure compensation can take place. Once sufficient medium has escaped from the container through the valve seat and the pressure in the container beneath the valve seat has again fallen, the valve closes as a result of the valve plate moving from the pass-through position into the closed position. For example, this occurs as a result of the gravitational force acting on said valve plate. The valve plate may additionally be spring-loaded, so that the closing force can be set freely, that is to say the force that must be overcome by the pressure prevailing in the container beneath the valve seat so as to bring the valve plate into the pass-through position.
If a suction relief valve is to be produced by means of the switching valve, the container in which the pressure may not fall below a predetermined response pressure is connected in the described arrangement to the region above the valve plate. If the pressure in the container falls below the predetermined response pressure, a force is thus also applied to the valve plate and moves the valve plate from the closed position into the pass-through position. The switching valve is thus opened and a pressure compensation is enabled between the container and the surrounding environment. Once the pressure in the container has risen above the predetermined response pressure, the force applied to the valve plate by means of the negative pressure in the container is no longer sufficient to hold the valve plate in the pass-through position, and the valve plate is thus brought into the closed position as a result of the closing force acting thereon.
So as to minimize material losses and therefore financial losses as well as environmental impact, it is important that the valve plate bears as tightly as possible against the valve seat via the valve plate face. In order to achieve this, different solution approaches are known in the prior art. For example, it is known to provide a resilient element, with which the tightness between the valve plate face and the valve seat is to be ensured. This resilient sealing element may be attached for example to the upper edge of the valve seat, that is to say the actual area contacting the valve plate face. Due to the closing force acting on this element when the valve is closed, the resilient sealing element deforms and thus ensures that the connection between the valve plate face and the valve seat is sealed.
Alternatively, a resilient element may also be provided in the edge region of the valve plate, where it has the same effect.
A valve plate is known from U.S. Pat. No. 3,394,732, with which an annular groove is provided in the edge region of the valve plate face and is spanned by a resilient sealing element. If a valve of this type is closed, the valve seat deforms the resilient element and presses it into the groove provided therefor. The connection between the valve plate face and the valve seat is sealed in this manner.
It is disadvantageous that the design of a valve plate of this type is relatively complex and therefore cost-intensive. In addition, the plastic layers proposed as the resilient sealing element, for example FEP films, can only be used to a limited extent within a temperature range between 60° and 150°, and are no longer usable thereabove since they leak and crease.
It is also known from the prior art to form a valve plate from a metal and to apply the valve plate directly via its valve plate face to the valve plate likewise consisting of metal. So as to sufficiently seal a connection of this type, both the valve plate and the valve seat have to be produced so as to be very flat. This makes the production method complex and therefore time-intensive and cost-intensive. The valve seat must therefore be ground and lapped so as to produce sufficient flatness. Valve seats or valve plates of this type normally have an unevenness of less than 10 μm.